RU2848478C1 - Knee joint endoprosthesis - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention refers to medicine, namely to traumatology and orthopaedics. Knee endoprosthesis includes a cushion insert and a body. Body is made of titanium alloy TNTZ in the form of an oval cylinder shaped after a seat of the tibial component, and comprises unloading windows for preventing excessive and negative pressure accumulation inside the body. Body is configured to fix the tibial component and the cushion insert and is rigidly fixed by screws on the tibial component. Tibial component is made of UHMWPE in the form of a platform, on one side of which there are grooves that are coupled along a cylindrical surface with arcs of the sleds of the femoral component. Tibial component is made of the titanium alloy TNTZ and represents a solid platform of an oval irregular shape. Shock-absorbing liner is made of a biocompatible polyurethane and follows the contour of the lower surface of the tibial component at 5 mm from the edge.

EFFECT: increased service life of endoprosthesis and increased comfort during physical loads.

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Description

Field of technology to which the invention relates

The invention relates to medicine, namely to traumatology and orthopedics, and can be used to restore the functions of knee joints subject to surgical intervention.

State of the art

It is known that knee joint arthroplasty (KJ) is performed when diseases such as:

- Stage III of the degenerative-dystrophic process,

- aseptic necrosis,

- inflammatory diseases of the joints and a number of other processes that destroy the joint [Voznitskaya O.E., Sabiryanov A.R., Atmansky I.A. Rehabilitation treatment for knee arthroplasty / Textbook for the system of postgraduate professional education, Chelyabinsk: Chelyabinsk State Medical Academy, 2009. - 79 p.].

The main goals in treating patients with knee joint lesions are: reducing pain intensity, restoring knee mobility and lower limb weight-bearing capacity. Various arthroplasty methods and devices are used for this purpose, such as endoprostheses with varying fixation. The degree of fixation is classified into 3 main types [Smetanin S.M. / Biomechanical justification for knee arthroplasty in structural and functional disorders: Abstract of a Doctor of Medicine dissertation: 14.01.15, Moscow: FGAOU VO First Moscow State Medical University named after I.M. Sechenov, 2018. - 48 p.]:

1) non-connected CR (Cruciate-retaining) is used when it is possible to preserve the posterior cruciate ligament, provided that it is intact and functional;

2) Semi-ligamentous PS (posterior stabilized), used for higher-level knee joint damage due to disease or injury, when the cruciate ligaments are completely removed. In this case, the endoprosthesis components are equipped with additional elements that perform an auxiliary function to stabilize the flexion/extension direction and limit the maximum flexion/extension angle of the limb;

3) The connected VVC (Varus Valgus Constrained) is a rigidly connected hinged joint with all components connected. This model is used for the most severe types of joint damage, as well as for the femur and tibia.

A known knee joint endoprosthesis (implant) is made in the form of solid components (femoral, tibial and tibial) [RU Patent 194174 dated November 29, 2019. Knee joint endoprosthesis / Rodionov I.V., Perinskaya I.V., Kuts L.E.], wherein: the femoral and tibial components are made of biocompatible, anti-corrosion, anti-friction alloys of Co, Cr, Ni, Ti, alloyed with Nb, Mo, Ti, Ta, Zr. The tibial component and patella are made of a polymer material, in particular ultra-high molecular weight polyethylene (UHMWPE).

The method of implantation of the endoprosthesis is carried out by resection of the condyles of the femur and tibia to the healthy tubular layer of bone with subsequent replacement of the resected areas with the components of the endoprosthesis [Patent of the Russian Federation No. 2187975 C1 dated 08.27.2002. Method of endoprosthetics of the knee joint / B.S. Bagnavets O.Sh., Buachidze V.P., Voloshin V.I., Dankov N.V., Zagorodniy B.S., Zubikov A.M., Nevzorov S.V., Sergeev D.A., Kholyavkin]. Disadvantages of the endoprosthesis: 1) its service life is limited, because after 10-20 years, the molecular bonds between the metal and bone tissue weaken under the influence of temporary dynamic loads with a vector transfer around the axis and back within 110°, accompanied by impact loads when walking, 2) a large difference in the elastic modulus of metal alloys and bone tissue (titanium alloys ≈ 110 GPa, chromium-nickel stainless steels ≈ 210 GPa, chromium-cobalt alloys ≈ 240 GPa, the elastic modulus of human bone is 50 ... 80 GPa), therefore, delamination of the fastening metal surfaces of the endoprosthesis from the bone occurs and revision endoprosthetics is required.

A tibial insert is known, placed on a base fixed or partially movable relative to the axis of the fastening rod (RU Patent No. 196434 dated 02.28.2020. Tibial component of a knee endoprosthesis / Byalik E.I., Pronskikh A.A., Brizhan L.K., Davydov D.V., Kornilov N.N., Khominets V.V., Makarov M.A., Kholyavkin D.A.). The design of the utility model allows for maximum bone tissue preservation due to a smaller sawdust thickness. In addition, the tibial plateau inclination angle of 4 degrees is optimized to improve the function of the preserved posterior cruciate ligament (PCL). The developed model is universal, since its design allows for the placement of inserts on a single tibial component both without stabilization (with the PCL preserved) and with varying degrees of stabilization. Furthermore, the design allows for an easy transition from primary to revision use on a single component through the use of augments designed to connect to the tibial component's anchor rod (stem). This model enables total knee arthroplasty for any knee pathology and any orthopedic abnormalities, including those associated with oncological diseases, and for any ligamentous condition. This design simultaneously reduces wear, reduces the weight of the structure, reduces traumatic complications, increases operational reliability and service life of the knee prosthesis, and reduces surgical time, improves processability, and enhances convenience. The model reproduces the mechanics of movement that occur in everyday life when performing the movements necessary for perfect knee joint function through the sliding and rolling of the component ends relative to each other.

A knee endoprosthesis with an internal microporous surface of the femoral component as a result of blistering pore formation is known (RU Patent No. 195379 dated 01.24.2020. Knee joint endoprosthesis / Rodionov I.V., Perinskaya I.V., Kuts L.E.). In the proposed femoral joint endoprosthesis, comprising a femoral component made in the form of a sled of two parallel arches fastened together, having on the inner side a support plane for the distal cut of the femur, a tibial component made in the form of a base, on opposite sides of which a limiter and a leg with stiffening ribs are fixed, a support pin, a platform made of UHMWPE, on one side of which recesses are made, mated along a cylindrical surface with the arches of the femoral component sled, and on the other side in the platform there are arcuate and guide grooves, in which the limiter and the support pin are installed, the sleds of the arches of the femoral component and the recesses in the platform mated with them are made in the form of cylindrical surfaces turning into tangent planes, each of which is located at an angle equal to 5-13° to the corresponding plane, parallel to the support plane of the distal cut of the femur and drawn through the corresponding line of contact. The inner surface of the femoral component of the endoprosthesis contains a microporous layer created by blistering pores during ion beam treatment with a helium (He+) ion beam. Ti, Ta, Zr, and their alloys can be used as materials for the manufacture of knee endoprostheses.

A knee endoprosthesis is known that includes a femoral component connected to a load-bearing tibial component via an insert configured to be secured at the base of the tibial component, wherein the femoral component of the knee endoprosthesis, made in the form of a single part, has a smooth outer load-bearing surface of a rounded shape with a variable sagittal radius of curvature on the posterior, distal and anterior sides of the component for an articulated connection with the load-bearing surface of the tibial component, an inner surface facing the femur; lateral and medial condylar elements that are separated on the posterior and distal sides by a gap corresponding to the intercondylar fossa in the natural knee joint with the possibility of placing cruciate ligaments; fixing pins placed on the side of the inner surface; reinforcing ribs located on the side of the inner surface and forming recesses for placing a layer of porous coating to form a physical connection with the femur, where the outer load-bearing surface on the anterior side of the femoral component is made in the form of a single surface formed by the convex surfaces of the lateral and medial condylar elements (RU Patent 197294 dated 04.20. 2020. Femoral component of a knee joint endoprosthesis / Byalik E.I., Pronskikh A.A., Brizhan L.K., Davydov D.V., Kornilov N.N., Khominets V.V., Makarov M.A., Kholyavkin D.A.).

A known knee endoprosthesis is one in which the femoral and tibial elements are made of VT 14 titanium alloy or cobalt-chromium alloy and coated with 0.5-1.5 μm of hard amorphous diamond-like carbon and an intermediate adhesive layer 0.05-0.15 μm thick made of titanium-carbon compounds (RU Patent 154362 of 20.08.2015. Coated knee endoprosthesis / Berdyugin K.A., Shlykov I.L., Makarova E.B., Rubshteyn A.P., Vladimirov A.B., Berdyugina O.V.). The surgery is performed using standard cementless fixation technology. After accessing the joint, bone growths and damaged areas are removed. The surface of the tibia and femur is prepared using special instruments. The endoprosthesis components are installed in their place using the press-fit fixation method. A UHMWPE liner is placed between the components.

Providing the surface of the femoral and tibial elements of the endoprosthesis in contact with bone tissue with a coating of hard amorphous diamond-like carbon with a thickness of 0.5-1.5 μm allows for surface strengthening (the surface hardness of the elements with the applied coating is 7000-10000 kg/ ^cm2 with a friction coefficient of no more than 0.1), while the carbon itself ensures maximum neutrality to the surrounding tissues of the body (Lifshits. Diamond-like carbon - present status. Diamond and related materials 8 (1999) 1659-1676, Cui FZ, Li DJ A review of investigations on the biocompatibility of diamond-like carbon and carbon nitride films. Surface and Coatings Technology, 131, 2000. - P. 481-487). The coating material of the femoral and tibial endoprosthesis is non-toxic and biocompatible with the surrounding tissues. The presence of an intermediate layer ensures optimal chemical interaction between the material of the knee joint endoprosthesis (VT 14 titanium or a cobalt-chromium alloy) and the hard amorphous diamond-like carbon, and its thickness is optimal for ensuring strong adhesion. The coating can be applied to the surface of the endoprosthesis components using known methods, such as plasma evaporation or condensation of 100 eV carbon ions generated by magnetron or arc sputtering of graphite.

The main disadvantages of the listed analogs are: 1) the service life of the implants is 10-20 years, depending on the quality of the surgery, rehabilitation and the absence of increased loads on the endoprosthesis, 2) limitation in physical activity and abandonment of the usual lifestyle, 3) high modulus of elasticity of metal alloys relative to the modulus of elasticity of human bone, 4) the absence of a shock-absorbing device.

The closest to the claimed one is the KJ endoprosthesis [RU Patent No. 179634 dated 06.10.2017. Knee joint endoprosthesis / Veselov S.V. et al.] - a prototype. The KJ endoprosthesis includes a femoral component, a tibial component with a supporting stem for fixation in the metaepiphysis of the tibia, and a removable polymer liner. The liner has a congruent surface for sliding contact with the articular surface of the femoral component and a rotating conical stem for sliding contact with a conical recess in the supporting stem of the tibial component. On the surface of the liner in contact with the articular surface of the femoral component, there are open pore channels in an amount of 5 to 25% of the sliding surface area, ranging in size from 0.1 to 200 μm. The main disadvantage is the lack of a shock-absorbing device.

Disclosure of invention

The proposed solution is applicable to the non-coupled type of endoprosthesis fixation and is aimed at solving the problem of creating a device - a knee joint endoprosthesis with a shock-absorbing insert that ensures the reduction of directed dynamic and impact loads falling on the connection of a metal alloy and bone tissue.

The technical result of the claimed invention consists in increasing the service life of the endoprosthesis and improving comfort during physical activity.

The technical result is achieved due to the fact that the knee joint endoprosthesis based on the femoral, tibial, tibial components, according to the solution, further comprises a shock-absorbing insert and a housing, the housing is designed with the possibility of fixing the tibial component and the shock-absorbing insert and is rigidly fixed with screws on the tibial component, the femoral component is made of titanium alloy TNTZ in the form of a sled of two parallel arcs fastened together, forming elements that replace the lateral and medial condyles and a supporting sliding surface for the patella, having on the inner side a supporting plane for the surfaces of the distal cut of the femur, the housing is made of titanium alloy TNTZ and is an oval cylinder repeating the shape of the seat of the tibial component, and includes unloading windows to prevent the accumulation of excess and negative pressure inside the housing, on the inner cylindrical surface of the housing in the upper part there is a groove for a polyurethane ring seal, the tibial component is made of UHMWPE in the form of a platform, on one side of which there are notches connected along the cylindrical surface with the arcs of the femoral component sleds, the tibial component is made of TNTZ titanium alloy and is a solid platform of an oval irregular shape, and the shock-absorbing insert is made of biocompatible polyurethane and follows the contour of the lower surface of the tibial component with an indentation from the edge of 5 mm.

The implementation of the technical problem is achieved by manufacturing an endoprosthesis (hereinafter EP) of the knee joint with a shock-absorbing insert, including:

The femoral component 1 for the non-connected type of EP is made of titanium alloy (TNTZ) Ti-29Nb-13Ta-4.6Zr [Biomaterials. July 2003; PMID: 12711513 DOI: 10.1016/s0142-9612(03)00069-3 / Mitsuo Niinomi] and is a solid part in the form of a sled made of two parallel arches fastened together, forming elements that completely replace the lateral and medial condyles and the supporting sliding surface for the patella, having a supporting plane on the inner side for the surfaces of the distal cut of the femur. On the mating surface of the EP of the distal cut there are two blind holes for the possibility of attaching two cylindrical guides 1.1 in them, which, during installation, are immersed in the holes for temporary fixation of devices for securing the conductor.

The tibial component 2 for the non-coupled type of EP is made of UHMWPE [Implants for surgery. Ultra-high molecular weight polyethylene. GOST 5834-2-2014; ISO 5834-2:2011] in the form of a platform, on one side of which recesses are made, mated along a cylindrical surface with the arcs of the sled of the femoral component. The sled of the arcs of the femoral component 1 and the recesses mated with them in the platform are made in the form of spherical surfaces turning into tangent planes, each of which is located at an angle of 5-13° to the corresponding plane parallel to the support plane of the distal cut of the femur and drawn through the corresponding line of tangency.

The housing 3 is made of titanium alloy TNTZ Ti-29Nb-13Ta-4.6Zr [Biomaterials. July 2003; PMID: 12711513 DOI: 10.1016/s0142-9612(03)00069-3 / Mitsuo Niinomi], and is an oval cylinder repeating the shape of the seat of the tibial component 4, fixed to it with two M4 screws (position 6) on the sides with a rounded recessed head for a hex key. Above the fastening screws are relief windows 3.1, which prevent the accumulation of excess and negative pressure within the housing 3. A groove for a polyurethane annular seal 5 is located on the upper part of the inner cylindrical surface of the housing 3. The seal is located between the housing 3 and the tibial component 4 and serves to reduce horizontal displacements under load, and also performs a protective function against the ingress of particles contained in the fluid in the joint capsule into the housing 3. The housing 3 acts as a connecting component during the movement of the tibial component 2 upon compression of the shock-absorbing insert 7. It serves as a position lock for the shock-absorbing insert 7.

The shock-absorbing insert 7 is made of biocompatible polyurethane [7.05.2014. PMID: 24812276 PMCID: РМС4230967 DOI: 10.1177/0885328214533737 / Hye Jin Kim, Min Sil Kang, Jonathan K. Knowles, Myung Sung Gon (Synthesis of highly elastic biocompatible polyurethanes based on bioisosorbide and poly(tetramethylene glycol) and their properties - PubMed (nih.gov))] follows the contour of the lower surface of the tibial component 2 with an indentation from the edge of 5 mm, laid for expansion during compression. It is installed between the tibial 2 and tibial 4 components, fixation from horizontal displacement and centering of the tibial component 2 is performed by the part - body 3.

The tibial component 4 is made of titanium alloy TNTZ Ti-29Nb-13Ta-4.6Zr [Biomaterials. July 2003; PMID: 12711513 DOI: 10.1016/s0142-9612(03)00069-3 / Mitsuo Niinomi] and is a solid platform of an oval irregular shape. The upper part has a flat step with a seat for the body part 3 and two holes with M4 threads on the sides for its fastening with screws 6. On the surface of the lower part of the component there is a rod 4.1, which performs fixation inside the tibia.

Brief description of the drawings.

The developed design of the implant is illustrated in Fig. 1-4, where:

Fig. 1 - a prototype of a knee joint endoprosthesis with a shock-absorbing insert, where: a - detailing of a 3D model of a non-connected type of fixation of the EP, developed in the Kompas 3D program, b - a printed 3D model of a non-connected type of fixation of the EP on a 3D printer;

Fig. 2 - calculation of the stress-strain state (SSS) of an implant under a load of 3000 N according to GOST 31621-2012, where the diagram on the right is the safety factor (FOS);

Fig. 3 - graph of the dependence of the safety factor (FOS) on the load of 2000...3000 N with an interval of 500 N;

Fig. 4 - experimental sample of the knee joint endoprosthesis with a shock-absorbing insert.

Implementation of the invention.

The primary mechanism that ensures the performance of the proposed knee joint endoprosthesis is a shock-absorbing liner, which is connected to the tibial and tibial components, forming a shock-absorbing unit that absorbs the bulk of the load under directed dynamic and impact loads, thereby relieving stress on the cementless fixation surfaces. This preserves the metal-bone bond and increases the service life of the implant.

An example of PM implementation.

Example 1. Evaluation of the safety factor in numerical modeling.

The implant's stress-strain state was analyzed using the Kompas 3D program under loads of 2000, 2500, and 3000 N, using static stress and safety factor calculations. The results are summarized in a single tabular and graphical form, showing the dependence of the indicators on changes in the applied load (Fig. 3).

Example 2. Manufacturing of a prototype implant.

The development of drawings and 3D prototype models in Kompas 3D models was carried out sequentially based on individual stages of implant design development. To verify the calculated data, each part of the product was created using a 3D printer based on the digital 3D model. ABS plastic was used to manufacture the components of the prototype implant.

Example 3. Clinical.

A knee replacement is installed as follows. Preoperative planning involves selecting the size of the replacement and the amount of bone resection using templates placed on knee X-rays.

Following the preparation, a total knee arthroplasty was performed. Surgical procedure: After a midline skin incision, the knee joint is opened via a medial parapatellar approach. The patella is dislocated laterally. After scar excision using standard techniques, the femur is debridement and the tibia is initially resected. A tibial component positioner is inserted into the lateral aspect of the knee joint along the lateral tibial condyle. Final debridement of the tibia is performed. After fitting, the final components of the endoprosthesis are installed. The tibial component is positioned precisely along the center of the tibial plateau. The wound is closed tightly in layers.

Claims (1)

A knee joint endoprosthesis based on femoral, tibial, and tibial components, characterized in that it additionally includes a shock-absorbing liner and a housing, the housing is configured to fix the tibial component and the shock-absorbing liner and is rigidly fixed with screws on the tibial component, the femoral component is made of TNTZ titanium alloy in the form of a sled of two parallel arcs fastened together, forming elements that replace the lateral and medial condyles and a supporting sliding surface for the patella, having on the inner side a supporting plane for the surfaces of the distal cut of the femur, the housing is made of TNTZ titanium alloy and is an oval cylinder repeating the shape of the seat of the tibial component, and includes unloading windows to prevent the accumulation of excess and negative pressure inside the housing, on the inner cylindrical surface of the housing in the upper part there is a groove for a polyurethane ring seal, the tibial component is made of UHMWPE in the form of a platform, on one side of which there are notches connected along the cylindrical surface with the arcs of the femoral component sleds, the tibial component is made of TNTZ titanium alloy and is a solid platform of an oval irregular shape, and the shock-absorbing insert is made of biocompatible polyurethane and follows the contour of the lower surface of the tibial component with an indentation from the edge of 5 mm.